Piling and pier inspection apparatus and method

ABSTRACT

The objects of the present invention are achieved by temporarily suspending sonar beam transducer means at a first underwater location within sonar beam range of said scoured area; scanning a first portion of said scoured area with said sonar beam in a first substantially vertical plane that points in a first azimuth direction, so as to generate signals indicative of the range and bearing of said scanned first portion from said transducer means; and scanning at least a second different portion of said scoured area with said sonar beam in a second different substantially vertical plane that points in a second different azimuth direction, so as to generate signals indicative of the range and bearing of said scanned second portion from said transducer means. In actual practice, scanning by the sonar beam occurs in many different vertical planes and also can be done from different underwater locations.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus using sonar fordetermining the nature of one or more scoured underwater bottom areasadjacent to structures submerged in a current of water. The invention isparticularly, but not exclusively, useful in safely determining thedepth and extent of such scoured areas when the water is moving at arelatively high velocity during flood conditions.

BACKGROUND OF THE INVENTION

Present day bridge structures reflect technological advances in designand construction that have evolved over the years. However, theseadvances have not precluded unfortunate and, in some instances, tragicoccurrences of bridge collapses resulting in the loss of life andproperty. Older bridges are even more prone to failure. These eventshave increased interest in the inspection and maintenance of bridges,prompting the U.S. Congress in 1968 to require the establishment ofnational bridge inspection standards (NBIS) and the development of aprogram to train bridge inspectors. In subsequent years, the governmenthas continued to stress the importance of bridge inspection and hasordered steps to insure that each state has a well-founded underwaterinspection program including scour investigations. Recent revisions tothe NBIS now mandate that a master list be developed of all bridgeswhich require underwater inspection, that procedures be determined forthese underwater inspections, and that the frequency of inspection foreach bridge (not to exceed 5 years) be determined.

Surveys indicate that there are hundreds of thousands of bridges in thecontinental United States which are over waterways of varying widths anddepths. Nearly one hundred thousand of these bridges must be monitoredfor scour conditions once every two years or more often if waterconditions, such as floods, dictate such inspection. A scour conditioncan arise when abnormally high or unusually fast flowing water in astream or river bed causes soil to be temporarily or permanently removedfrom various places in the river bottom, thus creating bottom holes ordepressions which may have substantial depth in relation to the averageelevation of the river bottom at these places. Although loose silt andother water-born materials may sometimes fill in a scoured area afterthe flood waters recede, this fill material often is less dense orcompacted than the previously undisturbed bottom soil and thus does notoffer as much lateral resistance as did the original soil. If suchscouring occurs around a supporting pier or footing of a bridge so as tosignificantly diminish the lateral restraining forces applied to thestructure by the surrounding soil, the potential exists for a failure ofthe structure after several scouring events have occurred. Thus, scourinspection is extremely important for bridge safety.

The two most common methods of scour inspection are manned divingoperations and small craft fathometer surveys. However, these methodsare usually practical for safety reasons only when the water is flowingless than about 3 feet per second. On the other hand, the most severescour conditions occur during flood stages where water can flow inexcess of 15 feet per second, which is when scour inspection is mostuseful in order to provide accurate data about the true extent of soilremoval. The reason for inspecting during flooding is that, as mentionedabove, loose silt may later refill a scoured area around a bridgefooting after the water subsides, which then may give a false impressionof soil conditions to a diver or to mechanical means for measuring theelevation of the river bed around bridge footings during a calm period.The present invention, however, is designed to function in fast flowingflood waters without posing danger to the personnel operating thissystem.

SUMMARY OF THE PRESENT INVENTION

Accordingly, it is a primary object of the present invention to providenovel methods and apparatus for safely ascertaining by sonar how muchscouring is taking place around bridges or similar structures when floodconditions prevail.

Another object of the present invention is to provide novel methods andapparatus for inspecting underwater scoured areas with sonar whereby nopermanent installation of equipment is required.

A further object of the present invention is to provide novel methodsand apparatus for quickly obtaining profile data about most, if not all,of an underwater area being scoured by high water velocity conditions.

These and other objects of the present invention are achieved bytemporarily suspending sonar beam transducer means at a first underwaterlocation within sonar beam range of said scoured area; scanning a firstportion of said scoured area with said sonar beam in a firstsubstantially vertical plane that points in a first azimuth direction,so as to generate signals indicative of the range and bearing of saidscanned first portion from said transducer means; and scanning at leasta second different portion of said scoured area with said sonar beam ina second different substantially vertical plane that points in a seconddifferent azimuth direction, so as to generate signals indicative of therange and bearing of said scanned second portion from said transducermeans. In actual practice, scanning by the sonar beam occurs in manydifferent vertical planes and also can be done from different underwaterlocations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic elevation view of a bridge structure over ariver bed which includes a simplified representation of the preferredinspection equipment used in the present invention.

FIG. 2 is a diagrammatic plan view of the FIG. 1 equipment and bridgestructure.

FIGS. 3, 4, and 5 are plan, side elevation and rear elevation views,respectively, of a first preferred embodiment of underwater sonarinspection scour fish apparatus used in the present invention.

FIG. 6 is a side elevation view of the bridge piers which also shows theorientation of the underwater sonar inspection apparatus.

FIG. 7 is a diagrammatic plan view showing the scanning procedure usinga sonar beam for the scoured areas around the bridge piers.

FIGS. 8A, 8B and 8C are diagrammatic elevation views taken along threeof the vertical scanning planes illustrated in FIG. 7.

FIGS. 9 and 10 are elevation and plan views, respectively, of a secondpreferred embodiment of a scour fish apparatus.

FIGS. 11 and 11A show another embodiment of the underwater sonarinspection apparatus, wherein the sonar head and its tilt-and-panmechanism are mounted on a finned structure which slides along a ropeattached to a bullet or clump weight.

FIG. 12 is a side elevation view showing how the first and second scourfish embodiments behave in similar surroundings.

FIGS. 13, 14, 15, and 16 are charts illustrating certain operatingcharacteristics of one or both of the first and second scour fishembodiments.

FIGS. 17 and 18 are side and end elevation views, respectively, of apreferred crane embodiment used to suspend the underwater sonarinspection equipment.

FIG. 19 is a diagrammtic representation of equipment in a remote surfacestation which is electrically connected to devices carried by theunderwater sonar inspection apparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

In describing the preferred embodiments of the subject inventionillustrated in the drawings, specific terminology is used for the sakeof clarity. However, the invention is not intended to be limited to thespecific terms so selected, and each specific term includes alltechnically equivalent terms for steps or devices operating in a similarmanner to accomplish a similar purpose.

FIGS. 1 and 2 (not to scale) are diagrammatic elevation and plan views,respectively, of a bridge structure over a river. This bridge structureconsists of a vehicle roadbed 10 supported at each end 11 and 12 by theembankments on each side of the river. The center part of the roadbedspan is supported by two pairs of spaced-apart piers 13A-13B and13C-13D, with the piers of each pair being positioned on opposite sidesof the roadbed 10 a best shown in FIG. 2. Each of the piers 13A-13D isvertically disposed and rests upon a respective footing 14A-14D, whichin turn is supported by several pilings 15 driven deep into the riverbottom 16.

As is partially observable in FIG. 1 which shows the downstream side ofthe bridge, it is assumed that the underwater bottom areas 17A and 17Cadjacent to the submerged footings 14 of the two downstream piers 13Aand 13C are being scoured to a depth below the average elevation of theriver bottom by virtue of a rapidly moving river current in thedirection of arrow 18 during a flood condition. Similar scouring is alsooccurring around the footings 14 of the two upstream piers 13B and 13D.In order to determine the nature of such scoured areas, such as theirdepth and extent, the present invention includes the use of equipmentnext to be described.

As shown in solid lines to the right of pier 13A in FIG. 1, anunderwater vehicle 19 (hereafter called a "scour fish" or "fish")carrying a sonar scanning head 20 is lowered from roadbed 10 by asupport rope or cord 21 into the water 22 and temporarily suspended atan underwater location (A). Rope 21 may be fed out and controlled by asuitable crane 23, whose boom 63 with reeving pulley 66 (see FIGS. 17and 18) is carried on a frame structure 24 that can be moved alongroadbed 10 on either side. This underwater scour fish 19, which is onlydiagrammatically shown in FIGS. 1 and 2, can be either one of twodifferent preferred embodiments such as are illustrated in FIGS. 3-5 orin FIGS. 9-10. The other dotted outlines of this fish 19, as shown inFIGS. 1 and 2, represent different underwater locations (B)-(F) to eachof which the fish may be successively moved and temporarily suspendedafter it has finished scanning scoured areas from its solid linelocation (A) shown in FIGS. 1 and 2.

FIGS. 3, 4 and 5 are plan, side elevation and rear elevation views,respectively, of a first preferred scour fish embodiment 19A at whosestern is attached the sonar scanning head 20. This 19A embodimentcomprises a body which includes a thin, flat laterally extendingdelta-shaped fixed wing structure 25 which is horizontally disposed andtapers inwardly toward the bow or front end of the fish. In practice,the fixed wing 25 can be about 48" wide from tip to tip. A thin verticalstabilizing fin 26 is connected to the rear half of the wing uppersurface and along the wing's longitudinal center line. A series of holes27 are formed in the fin 26 near its forward upper edge for attachingthe supporting rope 21 to the fish at any one of several positions bymeans of a pin 27a or other connector, depending on the dive angledesired for the fish.

A generally cylindrical bow weight 28 is attached under the front end ofwing 25 and to its lower surface for counter balancing the weight of thesonar head 20 and related equipment at the fish's stern. A shield 29 isalso attached to the wing lower surface and behind the bow weight 28 forenclosing and protecting a current flow meter 30 used to measure thevelocity of the swiftly moving river current at the fish's underwaterlevel. This current velocity information can be important to the enduser of the scour data when such data is being analyzed. Any suitablecurrent flow meter may be used, such as a Type 174 axial flow meteravailable from Endeco/YSI, Inc. Shield 29 has a screened window oropening 31 in front of the flow meter 30 for permitting the river waterto enter and activate the flow meter. This water exits through the openrear side of shield 29. The shield 29 is also tapered downwardly fromfront to back so that its lowest rear edge 32 extends below the sonarhead 20 in order to protect this head and its related equipment fromimpact damage caused by debris or other objects carried by the river.

The stern-mounted sonar scanning head 20, with a rotating transducer 33thereon, is connected to the rear lower surface of the wing 25 by meansof a rotatable tilt and panning mechanism 34. This tilt and panmechanism comprises (in part) a circular panning platform 35 which, inthe FIG. 4 elevation view, is rotatable in a horizontal plane about avertical axis by any suitable and conventional gear assembly that ismounted in a housing 36 and which is operably meshed with a gear on theshaft of an electrical panning motor 37 that is attached to the gearhousing 36. The sonar head 20 is secured by a U-shaped clamp 38 or othersuitable means to the undersurface of platform 35 so that the compass-pointing direction or azimuth of the scanning sonar head 20 can bechanged by the rotation of the platform. The gear housing 36, in turn,is suspended from ears or lugs 39 whose upper ends are fixedly connectedto the ends of a rotatable tilt shaft 40 that is horizontally disposedin the FIG. 4 and FIG. 5 elevation views. The tilt shaft 40 is containedin a tilt housing 41 secured to the delta wing lower surface at thefish's stern. An electrical tilt motor 42 is also mounted on the tilthousing 41 and has its motor shaft internally connected through anysuitable and conventional gear mechanism in said housing 41 to the tiltshaft 40 for rotating this shaft in either a clockwise or a counter-clockwise direction. Motors 37 and 42 obviously must be waterproofed byconventional techniques, and the same is true for gear housings 36 and41.

Transducer 33 is attached to the rotating horizontal shaft 46 of thehorizontal scanning sonar head 20, and this transducer generates a sonarbeam that impinges upon objects or surfaces in its path which reflectand return acoustic echo signals to the transducer. Transducer 33 thenconverts these acoustic return signals to electrical signals which areprocessed by suitable sonar equipment in a remote portable controlstation 43 on top of the bridge roadbed 10, or elsewhere if desired.FIG. 19 diagrammatically shows this sonar and other equipment in station43. The transducer 33 preferably generates a narrow angle conical sonarbeam 44 having a center line 45 which is illustrated in both FIG. 4 andFIG. 5. Beam 44 projects at a right angle from a flat face of thetransducer 33 which, as mentioned before, is mounted on the rotatingshaft 46 of the sonar head 20. As shown in FIG. 5, as the sonar headshaft 46 and transducer 33 rotate, the conical beam 44 also rotatesaround the shaft 46 as illustrated by the arrow 47. The sonar head 20may be programmed from the control station 43 to continuously rotate thetransducer 360° around its axis 46, or head 20 may be programmed tocause the transducer to scan a sector less than 360 degrees if this isall that is required for the scour inspection operation.

Sonar equipment suitable for the practice of the present invention maybe obtained from a variety of commercial sources. For example, theMesotech Model 971 sonar system (made by Mesotech Systems of PortCoquitlam, Canada) is particularly useful in this regard. Thus, thefunction of sonar head 20 in FIGS. 3-5 may be performed by the MesotechModel 971-1 rotary scanning head, while the transducer 33 shown in FIGS.3-5 may consist of the Mesotech Option 3 rotary scanning transducerwhich can generate either an imaging fan beam or a profiling cone beam.The Mesotech sonar cone beam is 1.7° in angular width and has a range upto 100 meters with a frequency of 675 kHz. Sonar head 20 is electricallyconnected via a multi-wire cable 48 (FIG. 1) to a Mesotech Model 971processor 50 in the control station 43 of FIG. 19, which also can housea Mesotech Model 971 monitor display unit 51 for viewing the processoroutput signals which provide target range and bearing information. InFIG. 4, this electrical cable 48 runs through the center of rope 21 and,although not specifically shown, is long enough to be connected to thevarious electrical components carried by fish 19A. Station 43 also caninclude a data storage means 52 for preserving these processor outputsignals which can later be used to generate the profiles of the scouredareas 17. Additionally, station 43 incorporates a control and viewingmeans 53 which is electrically connected with the tilt and pan mechanismon fish 19A, and further includes a current meter means 54 that iselectrically connected with the fish flow meter 30 for reading out theriver current velocity. A variable wing control means 55 is alsoelectrically connected with devices in a second preferred fishembodiment 19B to be described later in connection with FIGS. 9 and 10.

FIGS. 17 and 18 are side and end elevation views, respectively, of acrane apparatus 23 particularly suitable for storing and suspending thescour fish 19A of FIGS. 3-5 (and also scour fish 19B of FIGS. 9-10) inthe practice of this invention. This crane 23 primarily comprises anarticulated two-piece boom member which is mounted on a frame structure24, shown here to consist of a skid which can be easily transported by atruck or rail to the bridge site. The skid 24 also supports a powerpackage 56 which contains controls for operating the crane.

The lower crane boom member 57 is comprised of two spaced-apartelongated side members 57A and 57B whose bottom ends are respectivelypivoted on upstanding ears 58A and 58B which are mounted on a horizontaland rotatable ring gear platform 59 carried by the skid 24. The platform59 is changed in azimuth by a ring gear motor 60. A first hydraulic orair cylinder 61 and its associated piston 62 are connected between thering gear platform 59 and one lower boom side member 57A for applyingforce to rotate the lower boom 57 in a counterclockwise direction aboutits pivot points on the ears 58 so as to raise this boom to a verticalposition. The cylinder 61 and piston 62 also can be dimensioned tocontinue moving the boom 57 past the vertical to the other side of theears 58 from the position shown in the FIG. 18.

The top ends of the lower boom side members 57A and 57B are respectivelypivoted to the right ends (as shown in FIG. 18) of two spaced-apart sidemembers 63A and 63B which comprise the upper crane boom member 63. Asecond hydraulic or air cylinder 64 and its associated piston 65 areconnected between one lower boom side member 57A and one upper boom sidemember 63A for applying force to change the angle between said lower andupper booms 57 and 63 so that, for example, the upper boom 63 can bemade horizontal when the lower boom 57 is pivoted to a new position. Atotal working horizontal boom length up to 20 feet appears to befeasible without unduly increasing the size, weight or expense of crane23.

The reeving pulley 66 over which the fish support flexible line 21passes is rotatably carried on a shaft 67 between the upper boom sidemembers 63A and 63B near their left or free ends (as shown in FIG. 17).As is conventional with many reeving pulley systems, pulley 66 also canaxially slide back and forth on shaft 67 as this pulley rotates whensupport line 21 is pulled across it. A powered winch drum 68 forstoring, letting out and retrieving the support line is also affixed toa rotatable shaft 69 between the lower boom side members 57A and 57Bnear their upper ends, and this drum shaft 69 is rotated by a winchdrive motor 70 carried on the outside of one of these side members 57A.When the winch drum is rotated in a clockwise direction (FIG. 17) toreel in the support rope 21, the reeving pulley 66 moves back and forthalong its shaft 67 in order to evenly wind the support rope 21 acrossthe entire surface of the winch drum 68. If the support line 21 alsoincludes electrical cables within its hollow interior for communicationwith the fish, as described in connection with FIGS. 4 and 5, and alsowith FIGS. 9 and 10, these electrical cables may be unplugged from theremote station equipment when drum 68 is being rotated.

Finally, the left or free end of each upper boom side member 63A, 63Balso is provided with a downwardly extending V-strut standoff support71A and 71B (not shown), at whose bottom is attached a scour fishsupport pad 72A and 72B (not shown). These support pads 72 engage theupper body surface of the scour fish 19A (or 19B) when the support rope21 is completely retrieved and tightened, and they help to preventunwanted motion of the fish when the crane or its skid 24 is moved.

Although an articulated boom crane has been shown and described, othercrane or boom configurations (such as telescopic booms) may also be usedto deploy the scour fish.

The underwater orientation of the scour fish 19A is next described inconnection with the FIG. 6 side elevation view of bridge piers 13A and13B. This view also shows the fish suspended at its locations (A) and(D) Which, in practice, should preferably be about 11.5 feet below thewater surface if conditions permit. All of the other fish underwaterlocations also preferably should be about 11.5' deep if possible.Because of its delta wing 25 and stabilizing fin 26 configuration, thisfish remains in an extremely stable position and orientation when crane23 lowers it by rope 21 into a swiftly moving water current ofrelatively constant velocity so that its bow end faces upstream. Asshown in the left hand portion of FIG. 6, the fish's bow end at location(A) is depressed by the weight 28 and by the flow of water over the wing25, so that the fish's longitudinal axis along wing 25 forms a diveangle 25a with respect to the horizontal. This dive angle is somewhatdependent on where the rope 21 is attached to the fin 26 through one ofthe holes 27. Angle 25a also is larger for a higher current velocitywhich, in turn, would cause the fish to be located further downstreamfrom the pulley end of crane 23. Such an increase in the horizontaldistance between the crane boom pulley 66 and fish 19A will alsoincrease the angle 21a between rope 21 and the vertical. Thisrelationship between river current speed and the size of angle 21a isshown by the upper solid line 93 in FIG. 13 which will be describedlater. However, the fin 26 stays upright so that the wing 25 is notbanked to either side but remains generally horizontal except for thedive angle 25a given to it as previously described. The dashed outlineof fish 19A in the right hand portion of FIG. 6 represents a subsequentsuspended location (D) of the fish during the scour inspectionprocedure, during which time the fish is lowered by rope 21 from crane23 which has been moved to the upstream side of the bridge.

When the scour fish 19A assumes a stable dive angle 25a after beinglowered into a moving current of water, the tilt motor 42 is operated bycontrol means 53 via cable 48 from the remote control station 43 (FIG.19) in order to rotate the tilt shaft 40 in a counterclockwise directionso as to return the platform 35 to a horizontal plane position as shownin FIG. 6. This also causes the sonar head rotating axis 46 to lie in ahorizontal plane, notwithstanding the dive angle inclination of fish 19.The pan motor 37 may now be operated, via cable 48 from control means 53in the remote control station 43, in order to rotate the sonar head axisto any desired azimuth direction. Conventional tilt angle and azimuthsensing means may be included in the tilt and pan mechanism 34 forallowing the remote station operator to view and control theseparameters. For example, the mechanism 34 can be similar, if notidentical to, a Model PTE pan and tilt device made by the Remote OceanSystems company of San Diego, Calif.

FIGS. 7 and 8 diagrammatically illustrate the sonar scanning methodemployed by the present invention in order to generate data which can beused to develop a profile of the scoured areas 17 around each pier ofthe bridge. FIG. 7 is a simplified, diagrammatic plan view showing eachof the supporting piers 13, and a scoured area 17 around each of theirfootings 14 that needs to be examined during flood conditions.

Referring now to the lower right hand part of FIG. 7, it is assumed thatthe scour fish 19A (or 19B) has first been suspended in the water atlocation (A), as shown by its solid line position in FIGS. 1 and 2, sothat it is to the right and downstream of the pier 13A. It then isnecessary to ascertain more precisely where the fish and its sonar head20 are located with respect to a fixed point or points of reference sothat the sonar scour data can be correctly interpreted. The sonar head20 itself can be used to determine how far away it is in a plan viewfrom bridge structure, such as pier 13A, by scanning such structure inthe fashion illustrated in FIG. 1 after platform 35 has been madehorizontal and appropriately turned so that the transducer sonar beamcan strike such structure. If necessary for this purpose, the transducerscanning sector angle also can be made larger (up to a 360° sweep) thanis shown in FIG. 1. The vertical elevation of fish 19 (and its head 20),with reference to the bridge, can be determined by measuring the lengthof support rope 21 between crane pulley 66 and fish 19, and alsomeasuring the value of the support rope angle 21a shown in FIG. 6.

After the fish becomes stabilized at location (A) and its platform 35 ismade horizontal, this platform is now controlled from the remote station43 (FIG. 19) in order to turn the sonar head 20 so that its axis 46 andtransducer 33 point in an azimuth direction A₁, as shown in FIG. 7, inorder to start scanning the scoured areas 17. The transducer 33 is alsoset to sweep or rotate around the horizontal sonar head axis 46 througha sector scan angle of sufficient magnitude to cause its conical beam 44(represented by center line 45 in FIG. 7) to scan in a vertical planePA₁ and impinge upon most, if not all, of that portion of the riverbottom area which intersects or lies under said plane PA₁ within thebeam's effective range and line of sight. For example, the verticalsector scanning sweep of the sonar head transducer 33 at location (A)may be on the order of 120° as illustrated in FIG. 1, although only partof this sector sweep is shown in FIGS. 7 and 8 for the sake of clarity.Vertical sweep plane PA₁ is perpendicular to the FIG. 7 plan view, andit also points in an azimuth direction from location (A) that isperpendicular to direction A₁. Each point of beam impingement on theriver bottom is represented by a small circle 49. Although these circles49 are spaced apart in FIG. 7 for the sake of clarity, in practice theygenerally overlap because the conical beam 44 expands in diameter as ittravels away from transducer 33.

After the transducer 33 makes one or more sector scans in the verticalplane PA₁, the horizontal platform 35 is rotated a small amount in aclockwise direction so as to change the sonar head azimuth to adirection A₂ and cause the conical beam 44 to scan across anotherdifferent portion of the scoured area 17A in a slightly differentvertical plane PA₂ in FIG. 7. Plane PA₂ also points in another differentazimuth direction from location (A) that is perpendicular to A₂. Inpractice, the platform 35 preferably should be rotated only one or twodegrees at a time so that the bottom footprints 49 of the conical beam44 will impact on most of the scoured area 17A within the beam's rangeand sight line. This is partially illustrated in the FIG. 7 plan viewwhich shows only a few widely spaced different azimuth directions A₁,A₂, A₃, A₄, etc. for sonar head 20. The horizontal platform 35 with thesonar scanning head 20 is thus sequentially turned in small incrementalsteps until it finally reaches an azimuth direction A_(n) where theconical beam 44 no longer detects any portions of the scoured bottomarea 17A. Of course, platform 35 may be operated, if desired, to stepthrough a total azimuth angle which is wider than the angle between theillustrated directions A₁ and A_(n).

The elevation views in FIGS. 8A, 8B and 8C best illustrate the dataconveyed to and processed at the control station 43 by the conical beam44 as it scans the scoured area 17A around pier 13A. FIG. 8A is anelevation view taken perpendicular to the vertical scanning plane PA₂ inwhich the transducer conical beam 44 scans when sonar head 20 is at itsazimuth heading A₂. As the sonar head axis and transducer 33 rotate,conical beam pulses are generated which successively produce the beamcenter lines 45 shown in FIG. 8A. Thus, the sonar beam 44 marches acrossand impinges upon that portion of the river bottom, including part ofthe scoured area 17A, which is in line with or intersects the verticalbeam scanning plane PA₂. The reflected bottom return acoustic signalfrom each outgoing sonar conical beam pulse is detected by thetransducer 33 and processed by means 50 at control station 43 toindicate on the control station monitor 51 the range and bearing of eachbottom impact point 49 from the transducer for the particular scan angleoccupied by the transducer at the time it generated the outgoing beampulse. This information is also sent to the data storage device 52.

FIG. 8B illustrates the elevation profile of the portion of the riverbottom and scoured area lying under a different conical beam verticalscanning plane PA₃ when the sonar head is pointed to azimuth directionA₃ by the rotatable platform 35 on scour fish 19. As shown in FIG. 7,this vertical scanning plane PA₃ intersects a different portion of thescoured area 17A. Sonar data regarding the width and depth of thescoured area 17A underneath this vertical scanning plane PA₃ is thustransmitted to the sonar processing and storage equipment at controlstation 43.

In similar fashion, FIG. 8C illustrates another elevation profile viewof the river bottom, including a different portion of the scoured area17A, when the sonar head is again changed in azimuth to point indirection A₄ so as to scan in a vertical plane PA₄ that points in anazimuth direction which is perpendicular to A₄. As indicated earlier,the transducer 33 rotates on the sonar head axis 46 and emits a conicalbeam pulse at different angular positions which strikes a portion of theriver bottom and is reflected to provide information at station 43indicating the range and bearing of that bottom portion from thetransducer, as well as the transducer scan angle.

Thus, it will be seen that when the scour fish is at location (A), muchof the scoured area 17A around the pier 13A can be profiled bysequentially scanning various different portions of the scoured area oneafter the other. The scoured part not profiled at this time will be thearea behind the pier 13A which is not in a direct line of sight with thescanning sonar beam from location (A). Various portions of thisremaining 17A area, however, can be sequentially scanned when the fishis later moved to the location (B) shown in FIG. 7. At location (B), thesonar head 20 also can be panned in azimuth to scan the right hand partof scoured area 17C around pier 13C. The remaining left hand part ofarea 17C will be scanned when the fish is subsequently moved to location(C), not shown in FIG. 7 but illustrated in FIGS. 1 and 2.

Identical sonar scanning procedures are followed when the fish issubsequently moved to locations (D), (E) and then (F). For the sake ofclarity, FIG. 7 shows only a few of the azimuth scans by the sonar head20 at each of the locations (D) and (E), but it should be understoodthat many more azimuth scans are performed in order to allow the sonarbeam to impinge on most of the scoured areas 17B and 17D. If the sonarbeam has sufficient range when scanning from its upstream locations (D),(E), etc., it can also impact on the upstream portions of the downstreamscoured areas 17A and 17C in order to profile any of these areas thatmight remain hidden from the downstream scanning locations (A), (B),etc. In similar fashion, the sonar beam from its downstream locations(A), (B), etc., also may have sufficient range to sweep the downstreamportions of the upstream scoured areas 17B, etc., as is represented bythe extension of the beam center line 45 when sonar head 20 is pointedin the A_(n) direction from location (A). The profiling of the left handpart of scoured area 17D will be done when fish 19 is at location (F)shown in FIGS. 1 and 2.

Thus, the bottom range and transducer scan angle information thatappears on monitor 51 at station 43 is indicative of the scouring thatoccurs around the bridge piers during a flood condition. By observingthe monitor display for each azimuth direction, the station operator incomplete personal safety can make at least an initial determinationregarding the extent and possible severity of such scouring so as toform an opinion regarding the present or future safety of the bridge.Furthermore, the stored data can later be used to generate elevation andplan map views of the scoured areas.

In FIG. 7, it also is important to note that the horizontal positions ofthe upstream locations (D), (E) and (F) preferably should be such thatwhen the sonar transducer is totally facing downstream, the transducerface is on or upstream from a line tangent to the upstream ends of piers13B and 13D. This is advantageous and desirable because the sonar beamthen can sweep all of the upstream portions of scoured areas 17B and 17Dthat are adjacent to the pier upstream ends including the beginningportions of these scoured areas at points upstream from these piers. Onthe other hand, if scour fish locations (D), (E), and/or (F) werefurther downstream than as shown in FIG. 7, so that sonar head 20 islocated to one side of piers 13B and/or 13D (or is even locateddownstream from the downstream ends of these piers), then some portionsof these upstream scoured areas may be hidden by these piers from thesonar beam direct line of sight.

As is illustrated in the right hand portion of FIG. 6, the fixed wingscour fish 19A of FIGS. 3-5 is assumed to be lowered by support rope 21from a crane boom of some maximum effective length (e.g., 20 feet) to alocation (D) which is completely upstream from pier 13B when the bridgeroad bed 10 is not so high above the water's surface as to require anextremely long support rope 21, and when the river current velocity isnot so large as to substantially increase the rope angle 21a. However,FIG. 12 illustrates another upstream location (D) of this fixed wingfish 19A when a much longer support rope 21 is needed because the bridgeroadbed 10 is quite high above the water's surface, and/or when theriver flood current 18 is at or near maximum flood velocities up to 15knots so that the fish 19A is pushed farther downstream to therebyincrease the rope angle 21a to a fairly large value. For theseconditions, the fixed wing fish location (D) in FIG. 12 may undesirablybe to one side of a bridge pier 13B rather than being entirely upstreamtherefrom, unless the crane boom can be extended beyond its presentlyassumed maximum practical horizontal length of about 20 feet.

In FIG. 12 (not to scale), for example, assume (1) that the crane boomis at its maximum horizontal extension of 20 feet from the upstream endof pier 13B, (2) that the height of the boom reeving pulley 66 above thebridge roadbed 10 is about 10 feet, (3) that the height of the bridgeroadbed 10 above the flood water surface 22 is about 50 feet, (4) thatthe fixed wing fish 19A is located about 11.5 feet under the water'ssurface, and (5) that the flood river current speed is about 15 knots sothat the rope angle 21a for the fixed wing fish 19A is assumed to beabout 22° as shown by solid line 93 in FIG. 13. Under these conditions,the horizontal downstream distance of location (D) from the pulley endof the crane boom can be approximately calculated by multiplying thevertical distance between the boom pulley 66 and fish 19A (i.e., 10feet+50 feet+11.5 feet=71.5 feet) by the tangent of 22°. Thiscalculation results in a horizontal downstream distance of about 29 feetfrom the boom pulley 66 to the fish 19A, thus putting the fish location(D) about 9 feet downstream from the upstream end of the pier 13B. Thisdownstream position of location (D) might well prevent sufficient sonarscanning of the scoured area adjacent to the upstream end of the pier.

Accordingly, FIGS. 9 and 10 illustrate a second preferred embodiment 19Bof a scour fish which is more technically complex than the scour fish19A of FIGS. 3-5 but which can be used under all operating conditions ofbridge heights and current velocities that are expected to beencountered. As shown in the FIG. 9 elevation view and the FIG. 10 planview, this second scour fish embodiment 19B has a hollow body 73 whichincludes a laterally extending rounded nose or bow section 73A (in planview) which contains a weight 74 at its forward end. In the FIG. 10 planview, a second body section 73B of constant width extends rearwardlyfrom its nose section 73A, terminating in a squared stern end. The FIG.9 elevation view shows the fish body 73 to be slightly tapereddownwardly from its nose section 73A to a flow meter compartment 76which contains a flow meter 77. A window 78 in the body 73 permits waterto enter this compartment 76 for measurement of current velocity by theflow meter 77. The body section 73B back of compartment 76 is steppedupward and then rearward, as shown in FIG. 9, to provide a bottom aftsurface 79 on which is mounted a tilt and pan mechanism 34 with sonarhead 20 and transducer 33, all of which are identical in design andoperation to the correspondingly numbered components on the first scourfish embodiment 19A of FIGS. 3-5. The scour fish body 73 in FIGS. 9-10has slightly curved top and bottom surfaces, while its side surfacesalso are curved.

A thin, vertical center fin member 80 is mounted on the longitudinalcenter line of the rear part of the body top surface for alsostabilizing the fish 19B. A bracket with two upstanding ears 81A and 81Bis also secured on this center line of the body top surface at a forwardlocation from the fin 80. A pin 82 through the ears of this bracket isused to secure a braided support rope 21 having a hollow center, throughwhich passes the multi-wire electrical cable 48 from station 43 forcommunication with the various electrical components carried by the fish19B.

A pair of laterally extending trapezoidal (in plan view) and rotatablehollow wing members 83A and 83B also are fixedly attached to the ends ofa transverse shaft 84 which laterally extends through the fish body 73,one wing member being on each side of said body. Each wing structure inelevation is thicker than the diameter of shaft 84 and has roundedleading and trailing edges. A stabilizing thin vertical side fin member85A or 85B is also mounted on the upper surface of each wing near thewing's outer edge. Each side fin 85 is generally triangular in shapewith its apex located closer to the wing's trailing edge than to itsleading edge.

As shown by the broken-out section plan view of FIG. 10, shaft 84 isrotatably held by bearings 86 in the body side surfaces and is fittedwith a bull gear 87. This bull gear 87 engages a worm gear 88 which, inturn, is operably connected through a conventional gear box 89 with anelectric motor 90. The operation of motor 90 by the remote station 43operator will thus revolve shaft 84 and rotate the wings 83. In order tosecurely fix shaft 84 at a particular rotational angle for preventingcreep and undue stress on its motor gear train, a band type brake means91 is mounted on the shaft and operated by the electric brake controlmeans 92 that can be activated by the remote station operator. Thevariable wing control means 55 at station 43 (FIG. 19) may includeconventional motor controls.

By rotating these wing members 83 about the axis of shaft 84, the diveangle of the fish body 73 can be varied for any given velocity of watercurrent that is likely to be present during flood conditions. Variationof this dive angle will change the amount of horizontal force that isapplied by the current to the scour fish 19B, e.g., the smaller the diveangle, the smaller will be this force. In turn, the magnitude of thishorizontal moving water force will determine how far the fish ishorizontally moved by the current downstream from the end of the craneboom and, accordingly, what size angle 21a is formed between the supportrope 21 and the vertical. The remote station operator adjusts wings 83until he observes that a minimum angle 21a has been achieved.

Referring again to FIG. 13, the dashed line 94 represents the value ofthe support rope angle 21a for any given current speed to which thevariable wing scour fish 19B is exposed when its wings 83 areappropriately adjusted to minimize its dive angle at that speed. Theseangles 21a for the variable wing fish 19B are considerably smaller thanthe angles 21a for the fixed wing fish 19A as the current speedincreases. For example, at 15 knots the fixed wing support rope angle21a may be 22°, the support rope angle 21a may only be about 10° for thevariable wing fish if both fish embodiments are of comparable size(e.g., with about a 48" wing span). FIG. 12 also diagrammatically showshow this difference in support rope angle values will allow the variablewing fish 19B to occupy a location (D') which is totally upstream frompier 13B so as to insure complete sonar beam scanning of the scouredarea around the upstream edge of this pier. If the same hypotheticalvalues for boom height (10'), bridge height (50') and fish depth (11.5')are used for the variable wing fish 19B as were used in the precedingfixed wing fish example, the smaller 10° support angle 21a results infish 19B being horizontally located at (D'), which is only about 12.6'downstream from the boom pulley 66 as compared with the 29' downstreamdistance of location (D) for the fixed wing fish 19A. FIG. 15 also showshow a support angle 21a of 10° results in different horizontaldownstream distances from boom pulley 66 of the variable wing fish 19Bfor different values of bridge height above the water line (W.L.), e.g.,10 feet, 30 feet and 50 feet, when the fish depth (F.D.) is held atabout 11.5'.

Another advantage of the variable wing fish 19B over the fixed wing fish19A is shown by FIG. 14. For any given river current velocity, the pullor tension on support rope 21 is less for the variable wing fish 19Bthan for the fixed wing fish 19A, as shown by the lines 95 and 96. Thislesser pull permits a thinner and cheaper support rope to be used forthe variable wing fish 19B, or otherwise permits a longer life cycle fora variable fish's support rope of the same size. Furthermore, line 97 inFIG. 16 shows that when the upstream rope angle 21a is limited to amaximum value of about 10°, the crane boom length need not exceed 20'for complete upstream sonar coverage, even for a bridge which is 90'above the water surface (assuming a boom height of 10' and a fish depthof 11.5'). Of course, a lesser support rope angle of 5° (see line 98 inFIG. 16) will even more reduce the need for an extremely long and costlyboom when conducting upstream scour surveys.

FIG. 11 shows a different apparatus body for mounting and positioningthe sonar scanning head 20 used in the practice of this invention. Thetilt and panning mechanism 34 of FIGS. 3-5, which holds the sonarscanning head 20 and transducer 33, is also employed in FIG. 11 but isnot attached to a scour fish device. Instead, the mechanism 34 issecured to the underside of a thin vertical fin 99 whose upstreamvertical edge faces the current flow 18. Small laterally extending smalldelta-shaped wing structure 101A or 101B horizontally projects from eachside of fin 99 near its downstream vertical edge 102 in order to provideadditional resistance to banking. The plan view shape of these deltawings 101 is shown in FIG. 11A. The upstream vertical edge 100 of fin 99is attached by upper and lower ring couplers 103A and 103B to a verticalline 104 whose lower end is connected to a bullet or clump weight 105.This weight 105 is dropped over the side of the bridge above any one ofthe underwater locations (A)-(F) in FIG. 2 and pulls line 104 down untilthe weight strikes bottom. With the line 104 held taut by weight 105 andtension on the line 104 from above, the fin 99 with its attached sonarapparatus is then lowered to a position (A)-(F) along the line 104 by acombined support rope 106-electrical control cable 48 that is attachedto the fin 99. The fin 99 is aligned with the current direction 18 andremains stable in this position while the sonar head 20 scans thescoured bottom areas 17 in the manner previously described in connectionwith FIGS. 7 and 8. While not specifically shown in FIG. 11, controlcable 48 continues along fin 99 and reaches mechanism 34 and sonar head20 for establishing communication with remote station 43. Alternatively,fin 99 can be attached to a support rope 21, as in FIGS. 4 and 9, whereelectrical cable 48 runs through the center of rope 21.

Modifications and variations of the above-described embodiments of thepresent invention are possible, as appreciated by those skilled in theart in light of the above teachings. It is therefore to be understoodthat, within the scope of the appended claims and their equivalents, theinvention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A method of determining the nature of a secondunderwater bottom area adjacent to a structure submerged in a current ofrapidly moving water during a flood condition, said method comprisingthe steps of:(a) temporarily supporting sonar beam transducer means atleast at a first underwater location within sonar beam range of saidscoured area; (b) scanning a first portion of said scoured area with asonar beam from said first underwater location by sweeping said sonarbeam through an angle in a first substantially vertical scan plane thatpoints in a first azimuth direction from said first underwater location,so as to generate signals indicative of the range and bearing of saidscanned first portion from said transducer means at said firstunderwater location; and (c) scanning at least a second differentportion of said scoured area with a sonar beam from said firstunderwater location by sweeping said sonar beam through an angle in asecond different substantially vertical scan plane that points in asecond different azimuth direction from said first underwater location,so as to generate signals indicative of the range and bearing of saidscanned second portion from said transducer means at said firstunderwater location.
 2. Apparatus for determining the nature of ascoured underwater bottom area adjacent to a structure submerged in acurrent of water, said apparatus comprising:(a) sonar beam transducermeans; (b) means for temporarily supporting said transducer means at anunderwater location within sonar beam range of said scoured area; (c)means for causing said transducer means to scan a first portion of saidscoured area with a sonar beam which sweeps through an angle in a firstsubstantially vertical scan plane that points in a first azimuthdirection from said underwater location; (d) means for causing saidtransducer means to scan at least a second different portion of saidscoured area with a sonar beam which sweeps through an angle in a seconddifferent substantially vertical scan plane that points in a seconddifferent azimuth direction from said underwater location; and (e) meansresponsive to the sonar beam reflections from said first and secondscanned area portions to generate signals indicative of the ranges andbearings of said portions from said transducer means.
 3. The method ofclaim 1, wherein the sonar beam is conical in shape.
 4. The method ofclaim 1, in which said first and second scoured area portions aresequentially scanned one after the other.
 5. The method of claim 1, inwhich various different portions of said scoured area are sequentiallyscanned one after the other by the same sonar beam from said firstunderwater location, and wherein said first location scan of each saidportion is in a different substantially vertical scan plane that pointsin a different azimuth direction from said first location and which isless than ten degrees apart from the azimuth direction of an adjacentsubstantially vertical scan plane.
 6. The method of claim 5, wherein thesonar beam is conical in shape.
 7. The method of claim 1, which furthercomprises the steps of temporarily supporting sonar beam transducermeans at least at a second different underwater location within sonarbeam range of said scoured area and scanning various different portionsof said scoured area with a sonar beam from said second underwaterlocation so as to generate signals indicative of the ranges and bearingsof said portions from said transducer means at said second location,wherein said second location scan of each said portion is performed bysweeping said sonar beam through an angle in a different substantiallyvertical scan plane that points in a different azimuth direction fromsaid second underwater location.
 8. The method of claim 7, wherein thesame sonar beam transducer means that is supported at said firstunderwater location for scanning scoured area portions therefrom issubsequently moved to and supported at said second underwater locationfor scanning scoured area portions therefrom.
 9. The method of claim 8,wherein said sonar beam is conical in shape.
 10. The method of claim 5,which further comprises the steps of temporarily supporting sonar beamtransducer means at least at a second different underwater locationwithin sonar beam range of said scoured area and sequentially scanningvarious different portions of said scoured area with a sonar beam fromsaid second underwater location so as to generate signals indicative ofthe ranges and bearings of said portions from said transducer means atsaid second location, wherein said second location scan of each saidportion is performed by sweeping said sonar beam through an angle in adifferent substantially vertical scan plane that points in a differentazimuth direction from said second location and which is less than tendegrees apart from the azimuth direction of an adjacent substantiallyvertical scan plane.
 11. The method of claim 1, in which said firstunderwater location is upstream from said structure.
 12. The method ofclaim 1, wherein said transducer means is supported by a body that isspaced apart from said structure and which is suspended underwater byflexible line means attached to means above the water surface.
 13. Themethod of claim 12, wherein an angle is formed between said flexibleline means and the vertical which is not greater than about ten degrees.14. A method of determining the nature of a scoured underwater bottomarea adjacent to a structure submerged in a current of rapidly movingwater during a flood condition, said method comprising the steps of:(a)temporarily supporting sonar beam transducer means at an underwaterlocation upstream from said structure and within sonar beam range ofsaid scoured area, wherein said transducer means is supported by a bodythat is spaced apart from said structure and which is suspendedunderwater by flexible line means attached to means above the watersurface so that an angle is formed between said flexible line means andthe vertical which is not greater than about ten degrees; and (b)scanning at least the beginning portion of said scoured area upstreamfrom said structure with a sonar beam from said underwater location, soas to generate signals indicative of the range and bearing of saidscanned beginning portion from said transducer means at said underwaterlocation.
 15. The apparatus of claim 2, wherein said transducer meansgenerates a sonar beam which is conical in shape.
 16. The apparatus ofclaim 2, wherein said transducer support means comprises a body which issuspended underwater by means located above the water surface, said bodyincluding laterally extending delta-shaped structure that tapersinwardly toward an end of said body which faces upstream in said currentof water.
 17. The apparatus of claim 16, wherein said body furtherincludes laterally extending variable wing structure which is rotatableabout an axis laterally extending through said body.
 18. The apparatusof claim 16, wherein said sonar beam transducer means includes arotating transducer shaft, and said body is provided with tilt-and-panmeans to which said sonar beam transducer means is secured for makingsaid transducer shaft lie in a generally horizontal plane and forchanging the azimuth direction of said transducer shaft.
 19. Theapparatus of claim 18, wherein said transducer means generates a sonarbeam which is conical in shape.
 20. The apparatus of claim 18, whereinsaid body further includes laterally extending variable wing structurewhich is rotatable about an axis laterally extending through said body.